Subaru describes her as a girl that'd look good with a smile, yet he describes her "smile" as a smirk, and gave off the feeling that she made light of a lot of peoples' lives. She is also described to be evil intent in the shape of a child. Louis doesn't care much about what she eats, putting more emphasis on who she eats with. Also, the three speak in a collective manner using us and we instead of first or third person.

Being the youngest sibling, Louis initially​gives off the impression of being respectful and loving towards her brothers, but later reveals that she found them idiotic for blindly eating lives for her just because she was unable to exit the Corridor of Memories. Louis believes that life is unfair and is like a belt conveyor, without having the ability to choose the family, environment and future to be born into. Advocating her actions and beliefs as search for happiness, she mentions that she is doing effort to find the life that will satisfy her and let her live with her head held high, and currently believes that Subaru's​ life will provide her that fulfillment, as he is able to return by death, which will give her the ability to undo any mistakes she may make in future.

Authority of Gluttony (暴食の権能 Bōshoku no Ken'nō): Louis is able to use the Authority of Gluttony.

Gluttony (暴食 Bōshoku)

Louis can eat the name and memories of their opponent. To eat a name, she touches them with his left hand, then licks the palm of the same hand. Things such as experience, talent, and the likes and dislikes of human relationships serve as food for him, allowing him to take advantage of any abilities or memories his opponents had. However, if she eats a fake name, she becomes plagued with severe nausea.

Those that have had their names eaten have their existences erased from the world, destroying any human relationships along with preventing the use of magic and negating any contracts with Spirits.

Those that have their memories eaten become amnesic and any characteristics they may have had are reset, effectively making them into a different person.

Those that have both their name and memories eaten simply become a shell, and although they live, they no longer eat, excrete waste, or age, putting them in suspended animation.

Eclipse (蝕)

Eclipse is considered to be the trump card of gluttony and is also confirmed to have two types; Solar Eclipse (日食 Nisshoku) and Lunar Eclipse (月食 Gesshoku). The power of both haven't been entirely explained.

Lunar Eclipse (月食 Gesshoku): The madness and resentment around Ley deepened, which Otto described as becoming sinister on a different level, and his speed increased enough to make others feel as though she had moved in an instant. Louis, while speaking through Ley's body, claimed she couldn't use it properly in his current body but added that she could still completely destroy her opponents.

Solar Eclipse (日食 Nisshoku): Louis enters Ley's body while Ley's soul is put to sleep, and she is subsequently able to transform into people eaten by any of the Archbishops of Gluttony.

Master Class Fighter: Through accumulation of souls eaten, Louis gains any abilities her victims once had such as martial art techniques and magics except for Spirit Arts and Divine Protections. In turn this has granted her extraordinary combat strength.

Birthing: Louis mentioned that there would be problems in Giving Birth when she had transformed Ley's body.